Systems and methods for controlling operation of a valve

ABSTRACT

A solenoid valve includes a solenoid coil, a poppet, and a drive circuit. A first semiconductor device of the drive circuit is controlled by a gate signal to control a coil current. A flyback circuit of the drive circuit includes a second semiconductor device in series with a diode. The second semiconductor device is controlled by a flyback control signal to: (i) enable the flyback circuit to maintain the coil current through the solenoid coil when the poppet transitions to a second position, and (ii) disable recirculation of the coil current through the solenoid coil when the poppet transitions to a first position. A controller is configured to transition the poppet to the second position using the gate signal, enable the flyback circuit using the flyback control signal, and reduce at least one of a duty cycle and a frequency of the gate signal when the flyback circuit is enabled.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/703,427, filed on Dec. 4, 2019, which is a continuation of U.S.patent application Ser. No. 16/392,056, filed on Apr. 23, 2019, now U.S.Pat. No. 10,953,423, which claims priority to U.S. Provisional PatentApplication Ser. No. 62/661,344, filed on Apr. 23, 2018, the disclosuresof which are hereby incorporated by reference in their entirety.

BACKGROUND

The present disclosure relates generally to apparatus and methods fordispensing fluid and, more particularly, to fluid dispensing apparatusand methods using phased valves to control the emission of fluid throughfluid dispensing apparatus.

In the agricultural industry, fluid dispensing apparatus are used todispense agrochemicals. For example, some agrochemicals such as cropprotection agents and many fertilizers are applied as liquid solutions,suspensions, and emulsions that are sprayed onto the target fields.Certain agrochemicals, such as anhydrous ammonia, are dispensed intosoil through dispensing tubes positioned behind knives or plows thatprepare the soil for application.

Typically, the agrochemical liquid is supplied by powered pumps tonozzles and/or other dispensers connected to a distribution conduit.Pulse width modulation (PWM) of the liquid supplied to each spray nozzleis an alternative to system pressure variation for flow control and isnow a mature technology adopted in the U.S., Canada, and Australia. Forexample, known applications for PWM flow control systems are disclosedin U.S. Pat. No. 5,134,961 (Giles et al.), U.S. Pat. No. 5,653,389(Henderson et al.), U.S. Pat. No. 7,311,004 (Giles) and U.S. Pat. No.7,502,665 (Giles et al.) and U.S. Patent Application Publication Nos.2006/0273189 (Grimm et al.) and 2010/0032492 (Grimm et al.), all ofwhich are hereby incorporated by reference.

In a PWM flow control system, the fluid flow is interrupted in acontinuously cyclic timed sequence by an actuator positioned at thenozzle inlet. The fluid pressure may be essentially held constant at adesired value to achieve a desired droplet size spectrum during thepulsing flow control. Studies have shown that changes to droplet sizedistributions of modulated sprays are negligible and that PWM flowcontrol methods may be used as a form of droplet size control. BecausePWM flow control systems allow for flow rate changes at constantpressures, manipulation of the system pressure essentially acts as asystem-wide droplet size controller.

In such systems, valves are connected along the distribution conduit andcontrol discharge of the liquid from the distribution conduit andthrough the dispensers. The valves may be controlled individually or ingroups and may be pulsed between different positions to control the flowrate and other flow characteristics. However, the actuation of thevalves between an opened position and a closed position may cause unevenfluid flow through the distribution conduit, e.g., the liquid slosheswithin the distribution conduit. In addition, opening or closingmultiple valves at the same time may cause rapid pressure drops orspikes within the distribution conduit. Moreover, opening multiplevalves at the same time may result in a large instantaneous power drawon the electrical system.

Typically, operation of the valves is phased. For example, sometimes,some of the valves are moved to the opened position at a first timewhile the remaining valves are maintained in the closed position. Theremaining valves may be moved to the opened position at a second time.This phasing of the valves increases the operating efficiency of thefluid dispensing apparatus and reduces misapplication of the fluid.However, uneven fluid flow, pressure spikes, and current spikes maystill occur because the valves in each phase are actuated at the sametime. Accordingly, current valve phasing techniques may be less thanoptimal for certain applications.

Thus, a need currently exists for improved apparatus and methods forcontrolling agricultural dispensing systems including phased valves.

BRIEF DESCRIPTION

In one aspect, a solenoid valve is provided. The solenoid valve includesa solenoid coil, a poppet, and a drive circuit. The poppet is configuredto transition within the solenoid valve between a first position and asecond position based on a coil current flowing through the solenoidcoil. The drive circuit includes a first semiconductor device, and aflyback circuit. The first semiconductor device is controlled by a gatesignal to control the coil current. The flyback circuit is coupled withthe solenoid coil, and the flyback circuit includes a secondsemiconductor device in series with a diode. The second semiconductordevice is controlled by a flyback control signal to: (i) enable theflyback circuit to maintain the coil current through the solenoid coilabove a threshold value by recirculating the coil current through thesolenoid coil, the second semiconductor device, and the diode when thefirst semiconductor device is controlled by the gate signal totransition the poppet to the second position, and (ii) disablerecirculation of the coil current through the solenoid coil when thefirst semiconductor device is controlled by the gate signal totransition the poppet to the first position. A controller is configuredto transition the poppet from the first position to the second position,to enable the flyback circuit using the flyback control signal, and toreduce at least one of a duty cycle of the gate signal and a frequencyof the gate signal when the flyback circuit is enabled.

In another aspect, a method for controlling a solenoid valve having asolenoid coil and a poppet configured to transition within the solenoidvalve is provided. The method includes transitioning the poppet from afirst position to a second position using a gate signal applied to afirst semiconductor device coupled with the solenoid coil, where thefirst semiconductor device is controlled by the gate signal to control acoil current flowing through the solenoid coil. The method furtherincludes enabling a flyback circuit coupled with the solenoid coil, theflyback circuit including a second semiconductor device in series with adiode, where enabling the flyback circuit maintains the coil currentthrough the solenoid coil above a threshold value by recirculating thecoil current through the solenoid coil, the second semiconductor device,and the diode. The method further includes reducing at least one of aduty cycle of the gate signal and a frequency of the gate signal whenthe flyback circuit is enabled.

In another aspect, a drive circuit for controlling a solenoid valvehaving a solenoid coil is provided. The drive circuit includes a firstsemiconductor device, a flyback circuit coupled with the solenoid coil,and a controller. The first semiconductor device is controlled by apulse-width modulated (PWM) gate signal to energize the solenoid coiland transition the solenoid valve from a first position to a secondposition. The flyback circuit includes a second semiconductor device anda diode. The second semiconductor device is controlled by a flybackcontrol signal to: (i) enable the flyback circuit when the firstsemiconductor device is controlled by the PWM gate signal to hold thesolenoid valve in the second position, and (ii) disable the flybackcircuit when the first semiconductor device is controlled by the PWMgate signal to transition the solenoid valve to the first position. Thediode is coupled in series with the second semiconductor device to slowa decay of a current conducted through the solenoid coil while thesolenoid valve is in the second position. The controller is configuredto generate the PWM gate signal to transition the solenoid valve fromthe first position to the second position, to enable the flyback circuitusing the flyback control signal, and to reduce a duty cycle of the PWMgate signal when the flyback circuit is enabled.

These and other features, aspects and advantages of the presentdisclosure will become better understood with reference to the followingdescription and appended claims. The accompanying drawings, which areincorporated in and constitute a part of this specification, illustrateembodiments of the disclosure and, together with the description, serveto explain the principles of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an example agricultural fluid dispensingapparatus;

FIG. 2 is a perspective view of an example nozzle assembly suitable foruse with the agricultural fluid dispensing apparatus of FIG. 1;

FIG. 3 is a sectional view of a portion of an example valve assemblysuitable for use in the nozzle assembly shown in FIG. 2;

FIG. 4 is a schematic diagram of a control system suitable for use withthe fluid dispensing apparatus of FIG. 1;

FIG. 5 is a flow chart of an example method of dispensing fluid usingthe fluid dispensing apparatus shown in FIG. 1;

FIG. 6 is front view of a portion of a fluid dispensing apparatusincluding a distribution conduit and valve assemblies;

FIG. 7 is a graph showing valve position versus time for a fluiddispensing apparatus including a conventional phase offset;

FIG. 8 is a graph showing valve position versus time for a fluiddispensing apparatus including a phase offset and a sub-phase offset;

FIG. 9 is a plot showing the instantaneous number of open valves versustime for a fluid dispensing apparatus including a conventional phaseoffset and a fluid dispensing apparatus including a phase offset and asub-phase offset;

FIG. 10 is a graph showing valve position versus time for a fluiddispensing apparatus including a conventional phase offset for valvesoperated at sixty percent duty cycle;

FIG. 11 is a graph showing valve actuation versus time for a fluiddispensing apparatus including a phase offset and a sub-phase offset forvalves operated at sixty percent duty cycle;

FIG. 12 is a plot showing the instantaneous number of open valves versustime for a fluid dispensing apparatus including a phase offset forvalves operated at sixty percent duty cycle, and a fluid dispensingapparatus including a phase offset and a sub-phase offset for valvesoperated at sixty percent duty cycle;

FIG. 13 is a schematic diagram of a drive circuit for use in drivingsolenoid valves, such as the valve assembly shown in FIG. 3; and

FIG. 14 is a schematic diagram of another drive circuit for use indriving multiple solenoid valves and, particularly, phased solenoidvalves.

Corresponding reference characters indicate corresponding partsthroughout the several views of the drawings.

DETAILED DESCRIPTION

Referring now to the figures, FIG. 1 is a perspective view of an examplefluid dispensing apparatus, indicated generally at 10, operativelyconnected to a work vehicle 12. As shown, work vehicle 12 includes a cab14 and a plurality of wheels 16. Work vehicle 12 may, in certainembodiments, be an agricultural tractor having any suitableconfiguration. However, it should be appreciated that in otherembodiments, any other suitable aero or ground vehicle or means may beprovided for moving fluid dispensing apparatus 10. For example, in otherembodiments, work vehicle 12 may not include a cab, and instead may haveany suitable operator station. Further, in some embodiments, workvehicle 12 and/or fluid dispensing apparatus 10 may include a globalpositioning system (e.g., a GPS receiver) for automated control of workvehicle 12 and/or fluid dispensing apparatus 10. In some embodiments,the global positioning system is used to monitor a travel speed ofvehicle 12 and/or fluid dispensing apparatus 10, and/or to monitor aposition of work vehicle 12 and/or fluid dispensing apparatus 10.

In the example embodiment, fluid dispensing apparatus 10 is configuredto travel along a section of ground with a crop, produce, product or thelike (generally, P). Fluid dispensing apparatus 10 includes at least onedistribution conduit wheel 18, a tank or reservoir 22, and a spray boom24. Spray boom 24 includes a plurality of nozzle assemblies 34 attachedthereto and in fluid communication with tank 22. Tank 22 holds a productS, such as a liquid, a mixture of liquid and powder, or other product.Product S may be a quantity of water or an agrochemical such as afertilizer or a pesticide, and may be sprayed and dispensed from nozzleassemblies 34 onto, for example, a crop or produce, or on and/or intoground P itself, as shown in FIG. 1 and described in greater detailbelow. It should be appreciated, however, that in other embodiments,fluid dispensing apparatus 10 may have any other suitable configuration.For example, in other embodiments, fluid dispensing apparatus 10 may notinclude distribution conduit wheel 18 or may alternatively include anysuitable number of distribution conduit wheels 18. Further, while workvehicle 12 is depicted as towing fluid dispensing apparatus 10 in theexample embodiment, it should be appreciated that, in other embodiments,work vehicle 12 may transport fluid dispensing apparatus 10 in anysuitable manner that enables fluid dispensing apparatus 10 to functionas described herein. For example, in some embodiments, work vehicle 12may be an aerial vehicle and fluid dispensing apparatus 10 may beconfigured to spray fluid from a distance above the ground.

During operation of fluid dispensing apparatus 10, a quantity of productS held in tank 22 generally flows through one or more conduits to nozzleassemblies 34. More specifically, in the embodiment illustrated in FIG.1, product S flows from tank 22, through a pipe 30 to distributionconduit 32, and from distribution conduit 32 to nozzle assemblies 34. Itshould be appreciated that terms “pipe” and “conduit,” as used herein,may mean any type of conduit or tube made of any suitable material suchas metal or plastic, and moreover that any other suitable groundapplication devices can be added to provide varying effects of placementof product S on top or below a soil surface of ground P, such as viapipes, knives, coulters, and the like.

In certain embodiments, nozzle assemblies 34 comprise direct actingsolenoid valve equipped nozzles (see, e.g., FIGS. 2 and 3) and fluiddispensing apparatus 10 may include a pump, transducers to measure fluidpressure and fluid flow, sectional regulating valves, and a pressureand/or flow controller (not shown in FIG. 1). If included, the pump maybe positioned downstream from tank 22, upstream from distributionconduit 32 and nozzle assemblies 34, and in operative communication witha controller or control system of fluid dispensing apparatus 10. Thepump may be a pulse width modulation controlled pump configured toprovide a desired amount of product flow through fluid dispensingapparatus 10. The pressure or flow controller may be configured to varycertain operating parameters of the pump, such as the pump's pulsefrequency and/or duty cycle, to obtain a desired product flow ratethrough fluid dispensing apparatus 10. In alternative embodiments, fluiddispensing apparatus 10 may include one or more servo valves configuredto provide a desired amount of product flow through fluid dispensingapparatus 10.

Referring still to FIG. 1, product S flows through nozzle assemblies 34and may be applied to ground P in various ways. For example, product Smay flow from nozzle assemblies 34 in a pulsed pattern. A pulsed patternof fluid flow from nozzle assemblies 34 may allow for control of flowcharacteristics out of nozzle assemblies 34 and provide blendedapplication pulses to prevent skips and provide increased coverage ofthe fluid on ground P. As fluid flows from nozzle assemblies 34 in apulsed pattern, the instantaneous fluid flow within distribution conduit32 may vary. As described in more detail below, a sub-phase offset maybe utilized when nozzle assemblies 34 operate in a pulsed pattern toreduce or eliminate instantaneous pressure and flow fluctuations withindistribution conduit 32. As a result, fluid dispensing apparatus 10provides improved operating efficiency and accuracy of nozzle assemblies34 operating in a pulsed pattern. In addition, fluid dispensingapparatus 10 reduces spikes in electrical power consumption and problemsassociated with variations in instantaneous fluid flow, such as waterhammering, pressure fluctuations, and flowmeter inconsistencies.Further, as described in more detail below, current supplied torespective solenoid coils of the valves may be pulse-width modulated(PWM) at a relative high frequency to improve power efficiency and,moreover, may be combined with a controlled flyback circuit to furtherreduce average power consumption of the respective solenoid coils. Inyet other embodiments of the systems and methods described herein,utilizing sub-phase offsets, high-frequency PWM energizing of thesolenoid coils, and controlled flyback circuits may all be combined toachieve reduction in peak power consumption, decreased peak powerconsumption over time, and overall reduction in average powerconsumption by a given valve. Further, in such a combination, the systemwould exhibit improved operating efficiency of nozzle assemblies andmitigation of problems associated with varying instantaneous fluid flow,including water hammer, pressure fluctuations, and flowmeterinconsistencies.

For example, nozzle assemblies 34 may be grouped into a first sub-set ofnozzle assemblies 34 and a second sub-set of nozzle assemblies 34.Nozzle assemblies 34 in the first sub-set and nozzle assemblies 34 inthe second sub-set may be arranged in an alternating pattern alongdistribution conduit 32 such that each nozzle assembly 34 in the firstsub-set is separated from adjacent nozzle assemblies 34 in the firstsub-set by a nozzle assembly 34 in the second sub-set. Also, in sucharrangements, each nozzle assembly 34 in the second sub-set is separatedfrom adjacent nozzle assemblies 34 in the second sub-set by a nozzleassembly in the first sub-set. In alternative embodiments, nozzleassemblies 34 may be arranged in any manner that enables fluiddispensing apparatus 10 to operate as described herein. For example, insome embodiments, nozzle assemblies 34 in the first sub-set and thesecond sub-set may be grouped in sections along distribution conduit 32.In further embodiments, fluid dispensing apparatus 10 may include morethan two sub-sets of nozzle assemblies 34.

FIG. 2 is a perspective view of an example nozzle assembly 34 suitablefor use with fluid dispensing apparatus 10 of FIG. 1. As shown in FIG.2, nozzle assembly 34 generally includes a valve assembly 36, a nozzlebody 37 configured to receive product S flowing through distributionconduit 32 and a nozzle 39 mounted to and/or formed integrally withnozzle body 37 for expelling product S from nozzle assembly 34 ontocrops, product and/or ground P.

In some embodiments, valve assembly 36 is an electrically-actuatedsolenoid valve (see, e.g., FIG. 3). Moreover, in some embodiments, valveassembly 36 may be configured to be mounted to and/or integrated withnozzle 39 or nozzle body 37. In some embodiments, for example, valveassembly 36 may be mounted to the exterior of nozzle body 37, such as bybeing secured to nozzle body 37 through the nozzle's check valve port.Alternatively, valve assembly 36 may be integrated within a portion ofnozzle body 37. In other embodiments, valve assembly 36 may be mountedto fluid dispensing apparatus 10 separately from nozzle body 37 andconnected to nozzle body 37 by a conduit. In further embodiments, eachvalve assembly 36 may be coupled to a plurality of nozzles 39.

FIG. 3 is a simplified, cross-sectional view of an example electricsolenoid valve 300 suitable for use in valve assembly 36 shown in FIG.2. In general, valve 300 includes an inlet 302 and an outlet 304 forreceiving and expelling fluid 306 from valve 300.

Valve 300 also includes a solenoid coil 308 (shown in dashed lines)located on and/or around a guide 310. For instance, in one embodiment,solenoid coil 308 is wrapped around guide 310. Additionally, an actuatoror poppet 312 is movably disposed within guide 310. In particular,poppet 312 may be configured to be linearly displaced within guide 310relative to inlet 302 and/or outlet 304 of valve 300. Moreover, asshown, valve 300 includes a spring 314 coupled between guide 310 andpoppet 312 for applying a force against poppet 312 in the direction ofoutlet 304. It should be appreciated that valve 300 may also include avalve body or other outer covering (not shown) disposed around coil 308.

As shown in the illustrated embodiment, valve 300 is configured as acounter flow valve. Thus, fluid 306 may enter valve 300 through inlet302 along an axis 315 and exit valve 300 through outlet 304 along anaxis 316. Poppet 312 may be configured to be linearly displaced withinguide 310 along axis 316 such that fluid 306 may generally be directedout of valve 300 along axis 316. In other embodiments, valve 300 mayhave any configuration that enables fluid dispensing apparatus 10 tofunction as described. For example, in some embodiments, valve 300 isconfigured as an in-line valve. In other words, fluid may be configuredto enter and exit valve 300 along a common axis.

In addition, solenoid coil 308 may be communicatively coupled to acontroller 318 configured to regulate or control the current provided tocoil 308. Controller 318 may include one or more modules or devices, oneor more of which is enclosed within valve 300, enclosed within nozzleassembly 34, or located remote from nozzle assembly 34. Controller 318may generally comprise any suitable computer and/or other processingunit, including any suitable combination of computers, processing unitsand/or the like that may be communicatively coupled to one another(e.g., controller 318 may form all or part of a controller network).Thus, controller 318 may include one or more processor(s) and associatedmemory device(s) configured to perform a variety of computer-implementedfunctions (e.g., performing the methods, steps, calculations and/or thelike disclosed herein). As used herein, the term “processor” refers notonly to integrated circuits referred to in the art as being included ina computer, but also refers to a controller, a microcontroller, amicrocomputer, a programmable logic controller (PLC), an applicationspecific integrated circuit (ASIC), a digital signal processor (DSP), afield programmable gate array (FPGA), and other programmable circuits.Additionally, the memory device(s) of controller 318 may generallycomprise memory element(s) including, but not limited to, non-transitorycomputer readable medium (e.g., random access memory (RAM)), computerreadable non-volatile medium (e.g., a flash memory), a floppy disk, acompact disc-read only memory (CD-ROM), a magneto-optical disk (MOD), adigital versatile disc (DVD) and/or other suitable memory elements. Suchmemory device(s) may generally be configured to store suitablecomputer-readable instructions that, when implemented by theprocessor(s), configure controller 318 to perform various functionsincluding, but not limited to, controlling the current supplied tosolenoid coil 308, monitoring inlet and/or outlet pressures of thedisclosed valve(s), monitoring poppet operation of the disclosed valves,receiving operator inputs, performing the calculations, algorithmsand/or methods described herein and various other suitablecomputer-implemented functions.

Coil 308 may be configured to receive a controlled electric current orelectric signal from controller 318 such that poppet 312 may move withinguide 310 relative to outlet 304. For example, in one embodiment,controller 318 includes a square wave generator, a coil drive circuit,or any other suitable device that is configured to apply a regulatedcurrent to coil 308, thereby creating a magnetic field which biases (byattraction or repulsion) poppet 312 away from outlet 304. As a result,poppet 312 may be moved between a closed position and an openedposition. One exemplary agricultural spray system may operate valves,such as valve 300, at about 10 Hertz, i.e., a given solenoid valve isopened every 100 milliseconds (ms) according to a valve-pulsing PWMsignal. For certain operating pressures, the solenoid valve may takeabout 6 ms to open from the time coil 308 is energized, and about 4 msto close from the time coil 308 is de-energized. For the remainder ofthe 100 ms period, the solenoid valve maintains the poppet in the openedor closed position, otherwise referred to as idle time. Typically, whena solenoid valve is activated, i.e., opened and held open, the solenoidcoil is energized continuously and, conversely, when the solenoid valveis deactivated, i.e., closed and held close, the solenoid coil isde-energized. Alternatively, the frequency and duty cycle of the currentconducted through the solenoid coil may be regulated to continuouslyconduct current through the solenoid coil while maintaining control ofthe desired valve-pulsing PWM signal.

In some embodiments, coil 308 may be driven with a complex pulsedvoltage, or PWM waveform. A “pulse” may correspond to a duration (e.g.,a 100 millisecond cycle) in which a low frequency duty cycle value setsthe amount of on/off time. The “on” time may correspond to a “coildischarging (or charging) period” in which the drive voltage is turnedoff (or on) continuously and a “modulated period” in which the voltageis turned on and off at a high frequency (e.g., at a frequency ofgreater than 200 Hz). The duration of the coil discharging (or charging)period, also referred to as the “turn-on time”, may be determined by theamount of time for the coil current to reach the desired value. The coilcurrent may be continuously measured and compared to a threshold totrigger switching of the drive voltage to a modulated signal. Controller318 may use a stored threshold and/or a threshold determined based onoperating parameters of fluid dispensing apparatus 10 (shown in FIG. 1).For example, in some embodiments, the threshold may change duringoperation of fluid dispensing apparatus 10 based on information from asensor that detects a position of poppet 312. In further embodiments,the threshold is determined based on the fluid pressure against poppet312 and the current required to move poppet 312 to the open positionand/or to move poppet 312 to the closed position.

In certain embodiments, controller 318 may control the supply of currentto coil 308 to move poppet 312 to a throttling position intermediate thefully-opened and fully-closed position to control the instantaneouspressure drop across valve 300. Additionally, the attraction betweencoil 308 and poppet 312 may also allow poppet 312 to be pulsated orcontinuously cyclically repositioned, thereby providing for control ofthe average flow rate through valve 300.

In several embodiments, when valve 300 is being pulsed, the movement ofpoppet 312 may be cycled between the opened position and a closed, orsealed, position, wherein poppet 312 is sealed against outlet 304. Thus,as shown in FIG. 3, poppet 312 may also include one or more rubber disksor other suitable sealing members 320 that is configured to be pressedagainst outlet seat 322 of outlet 304 to create a leak-free seal whenvalve 300 is in the sealed position. A projection 328 extending fromsealing member 320 may be received in outlet 304 when valve 300 is inthe sealed position.

FIG. 4 is a schematic diagram of a control system 110 suitable for usewith the fluid dispensing apparatus of FIG. 1. Control system 110includes controller 318 communicatively connected toelectrically-actuated nozzle assemblies 34. In the illustratedembodiment, fluid dispensing apparatus 10 includes a first nozzleassembly 134, a second nozzle assembly 136, a third nozzle assembly 138,and a fourth nozzle assembly 140 arranged sequentially alongdistribution conduit 32. First nozzle assembly 134 and third nozzleassembly 138 are included in a first sub-set of nozzle assemblies.Second nozzle assembly 136 and fourth nozzle assembly 140 are includedin a second sub-set of nozzle assemblies. Each nozzle assembly 134, 136,138, 140 includes a valve assembly, such as valve assembly 36. It shouldbe understood that fluid dispensing apparatus 10 may include any typeand number of nozzle assemblies that enables fluid dispensing apparatus10 to function as described herein. For example, in some embodiments,fluid dispensing apparatus 10 may include three or more sub-sets ofnozzle assemblies. In further embodiments, first nozzle assembly 134,second nozzle assembly 136, third nozzle assembly 138, and fourth nozzleassembly 140 are not arranged sequentially along distribution conduit32. For example, in some embodiments, first nozzle assembly 134 may bepositioned at a middle of distribution conduit 32. Second nozzleassembly 136, third nozzle assembly 138, and/or fourth nozzle assembly140 may be positioned on either side of first nozzle assembly 134.

Controller 318 is communicatively connected to each nozzle assembly 134,136, 138, 140 and is configured to cause actuation of valve assemblies36 of respective nozzle assemblies 134, 136, 138, 140 in phases andsub-phases. For example, controller 318 is configured to determine aphase offset to separate actuation of the subsets of nozzle assemblies134, 136, 138, 140 into phases. Specifically, the first sub-set ofnozzle assemblies 134, 138 are actuated in a first phase and the secondsub-set of nozzle assemblies 136, 140 are actuated in a second phaseseparated from actuation of the first phase by the phase offset. In someembodiments, controller 318 may include a plurality of distributed unitsconnected to or integrated into individual valve assemblies 36. In suchembodiments, controller 318 may include a centralized unit connected toeach of the distributed units and/or valve assemblies, or may notinclude a centralized unit.

In addition, controller 318 is configured to determine a sub-phaseoffset to separate actuation of nozzle assemblies 134, 136, 138, 140within each of the first sub-set and the second sub-set into sub-phases.For example, in the first phase, actuation of first nozzle assembly 134is separated from actuation of third nozzle assembly 138 by thesub-phase offset. In the second phase, actuation of second nozzleassembly 136 is separated from actuation of fourth nozzle assembly 140by the sub-phase offset. Accordingly, each nozzle assembly 134, 136,138, 140 is actuated at a different time. As a result, fewer valves areopened and closed simultaneously within fluid dispensing apparatus 10 ascompared to fluid dispensing apparatus using conventional valve phasing,and fluctuations in instantaneous fluid flow within distribution conduit32 are reduced. In the exemplary embodiment, nozzle assemblies 134, 136,138, 140 are actuated such that none of the valves are opened and closedsimultaneously within fluid dispensing apparatus 10. In alternativeembodiments, nozzle assemblies 134, 136, 138, 140 may grouped insections along distribution conduit 32 and more than one nozzle assembly134, 136, 138, 140 may be actuated simultaneously. For example, in someembodiments, each of the first and second valve sub-sets may include aplurality of groups or “gangs” of valves (also referred to as “ganged”valves), where all of the valves within a respective group of valves areactuated in unison or simultaneously (i.e., as a single unit). In suchembodiments, the groups or “gangs” of valves within one of the first andsecond valve sub-sets may be actuated out-of-phase from one another bythe sub-phase offset, instead of individual valves within a valvesub-set being actuated out-of-phase by the sub-phase offset. In suchembodiments, the valve sub-sets may instead be referred to as “valvesets”, and the groups or gangs of valves within the valve sets may bereferred to as “valve sub-sets”. The various valve actuation and phasingtechniques described herein are equally applicable to such groups or“gangs” valves, and may be implemented with such embodimentsaccordingly.

Each valve assembly 36 of nozzle assemblies 134, 136, 138, 140 may bepulsed according to a duty cycle and a cycle time. Accordingly,controller 318 may determine the phase offset based on the cycle timeand the number of nozzle assemblies 134, 136, 138, 140. For example, thephase offset may be determined by dividing the cycle time by the numberof valve sub-sets. In addition, controller 318 may determine thesub-phase offset based on the number of the plurality of valves and acycle time of the valves. Specifically, the sub-phase offset may bedetermined by dividing the cycle time by the number of the plurality ofvalves. In alternative embodiments, the phase offset and the sub-phaseoffset may be determined in any manner that enables fluid dispensingapparatus 10 to function as described herein. For example, in someembodiments, the sub-phase offset may be determined based on the numberof active nozzle assemblies. In other words, in such embodiments, nozzleassemblies 134, 136, 138, 140 that are in a closed position and are notbeing actively pulsed may not be included in the calculation fordetermining the sub-phase offset. In addition, in some embodiments,controller 318 may determine the sub-phase offset based oncharacteristics of fluid flow within distribution conduit 32 such asfluid pressure. In further embodiments, controller 318 may determine thesub-phase offset based on a cycle time of valve assemblies 36, thenumber of valve assemblies 36, the configuration of piping connected tovalve assemblies 36, and/or a duty cycle of valve assemblies 36. Forexample, in some embodiments, one or more of valve assemblies 36 may bepulsed at different duty cycles. For example, each valve assembly 36 maybe pulsed at a different duty cycle to compensate for varying speedsalong the distribution conduit when fluid dispensing apparatus 10 isbeing turned. In such embodiments, the phase offset and/or sub-phaseoffset may be determined based on the duty cycle of each valve assembly36, the number of valves assemblies 36, and/or the cycle time of eachvalve assembly 36. In some embodiments, controller 318 may determineand/or change the phase offset and/or the sub-phase offset at any timeduring operation of fluid dispensing apparatus 10.

In some embodiments, the order of actuation of the nozzle assemblies134, 136, 138, 140 is determined based on the position of the respectivenozzle assemblies 134, 136, 138, 140 along distribution conduit 32. Inalternative embodiments, the valve assemblies 36 may be actuated in anyphases and/or sub-phases that enable the fluid dispensing apparatus 10to operate as described herein. For example, the number of phases, thenumber of sub-phases, and/or the actuation frequency (number ofactuations per cycle time) may be determined at least in part based onthe intended use (e.g., ground sprayer, aerial sprayer, anhydrousfertilizer dispenser) of fluid dispensing apparatus 10.

In some embodiments, each nozzle assembly 134, 136, 138, 140 or eachgroup of ganged nozzle assemblies 134, 136, 138, 140 is included in aseparate or unique phase, and actuation of individual nozzle assemblies134, 136, 138, 140 or groups of ganged nozzle assemblies 134, 136, 138,140 are separated by the phase-offset. In other words, a unique phasemay be determined for each nozzle assembly or valve (or each group ofganged valves or nozzle assemblies) within the fluid dispensingapparatus 10.

During operation of fluid dispensing apparatus 10, product S flows froma centrifugal pump 128 to a flow regulating valve 172 via a pressurepipe 170. The flow regulated product S flows to a flow meter 162, to apressure sensor 152, and to nozzle assemblies 134, 136, 138, 140 viadistribution conduit 32. In some embodiments, controller 318 may receivetarget rate information from a rate input device 168 and travel speedfrom a speed input device 166. Controller 318 sequentially actuatesvalve assemblies 36 of nozzle assemblies 134, 138 in the first sub-setbased on the sub-phase offset such that actuation of each nozzleassembly 134, 138 in the first sub-set is out of phase from actuation ofeach preceding nozzle assembly 134, 138 in the first sub-set by thesub-phase offset. Controller 318 sequentially actuates valve assemblies36 of nozzle assemblies 136, 140 in the second sub-set based on thephase offset and the sub-phase offset such that (i) each nozzle assembly136, 140 in the second sub-set is actuated out of phase from an adjacentnozzle assembly 134, 138 in the first sub-set by the phase offset; and(ii) each nozzle assembly 136, 140 in the second sub-set is actuated outof phase from each preceding nozzle assembly 136, 140 in the secondsub-set by the sub-phase offset. During the phased pulsing, nozzleassemblies 134, 136, 138, 140 dispense fluid from fluid dispensingapparatus 10. Although valves or nozzle assemblies in the second sub-setare described as being actuated out-of-phase from an adjacent valve ornozzle assembly in the first sub-set by the phase offset, it should beunderstood that, in certain embodiments, valves or nozzle assemblies inthe second sub-set may be actuated out-of-phase from a preceding,non-adjacent valve in the first sub-set by the phase offset.

In some embodiments, controller 318 may actuate multiple nozzleassemblies 34 simultaneously, i.e., the nozzle assemblies 34 may beganged. For example, at least some nozzle assemblies 34 in the firstsubset and/or the second subset may be ganged such that at least onegroup of nozzle assemblies 34 in the first sub-set and/or the secondsub-set are actuated together. Accordingly, controller 318 maysequentially actuate groups of valve assemblies 36 of nozzle assemblies136, 140 in the second sub-set based on the phase offset and thesub-phase offset such that (i) each group of nozzle assemblies 136, 140in the second sub-set is actuated out of phase from an adjacent orpreceding group of nozzle assemblies 134, 138 in the first sub-set bythe phase offset; and (ii) each group of nozzle assemblies 136, 140 inthe second sub-set is actuated out of phase from each preceding group ofnozzle assemblies 136, 140 in the second sub-set by the sub-phaseoffset.

FIG. 5 is a flow chart of an example method 200 of distributing fluid,such as product S, using fluid dispensing apparatus 10. In the exampleembodiment and with reference to FIGS. 4 and 5, method 200 includessupplying 202 fluid to distribution conduit 32 of fluid dispensingapparatus 10. In some embodiments, centrifugal pump 128 pumps product Sfrom tank 122 and product S is delivered to distribution conduit 32. Inalternative embodiments, fluid may be supplied to distribution conduit32 in any manner that enables fluid dispensing apparatus 10 to operateas described herein.

In addition, method 200 includes determining 204 a phase offset toseparate actuation of the plurality of valve sub-sets into phases anddetermining 206 a sub-phase offset to separate actuation of valveassemblies 36 within each of the plurality of valve sub-sets. In someembodiments, controller 318 determines the phase offset based on thenumber of sub-sets and the cycle time of valves. Specifically,determining 204 the phase offset may include dividing the cycle time bythe number of valve sub-sets in the plurality of valve sub-sets. Inaddition, in some embodiments, controller 318 determines the sub-phaseoffset based on the number of valve assemblies 36 and a cycle time ofvalve assemblies 36. Specifically, determining 206 the sub-phase offsetmay include dividing the cycle time of the valves by the number of theplurality of valves. In alternative embodiments, the phase offset and/orthe sub-phase offset may be determined in any manner that enables fluiddispensing apparatus 10 to function as described herein. In someembodiments, the phase offset and/or the sub-phase offset are at leastpartially determined based on user inputs.

In some embodiments, method 200 may include determining a plurality ofsub-phase offsets. For example, a first sub-phase offset may bedetermined to separate actuation of the valves within the first sub-setand a second sub-phase offset may be determined to separate actuation ofthe valves within the second sub-set. In further embodiments, the secondsub-phase offset is equal to the first sub-phase offset. In addition, insome embodiments, the first sub-phase offset and/or the second sub-phaseoffset is varied during actuation of valve assemblies 36.

Also, method 200 includes sequentially actuating 208 valve assemblies 36in the first sub-set based on the sub-phase offset. Accordingly, eachvalve assembly 36 in the first sub-set is actuated out of phase fromeach preceding valve assembly 36 in the first sub-set by the sub-phaseoffset. Method 200 further includes sequentially actuating 210 valveassemblies 36 in the second sub-set based on the phase offset and thesub-phase offset. As a result, each valve assembly 36 in the secondsub-set is actuated out of phase from an adjacent or preceding valveassembly 36 in the first sub-set by the phase offset. In addition, eachvalve assembly 36 in the second sub-set is actuated out of phase fromeach preceding valve assembly 36 in the second sub-set by the sub-phaseoffset. Actuation of valve assemblies 36 may include pulsing each valveassembly 36 according to a duty cycle and a cycle time. In alternativeembodiments, valve assemblies 36 may be actuated in any manner thatenables fluid dispensing apparatus 10 to operate as described.

Actuation of valve assemblies 36 results in fluid, such as product S,being dispensed from nozzle assemblies 134, 136, 138, 140. The phasedactuation of valve assemblies 36 increases the accuracy and operatingefficiency of fluid dispensing apparatus 10. For example, the phaseoffset provides a more consistent application of product S and thesub-phase offset reduces variations in instantaneous flow rate indistribution conduit 32 and distributes the instantaneous power draw onthe electrical system of fluid dispensing apparatus 10.

FIG. 6 is a front view of a portion of a fluid dispensing apparatus 400including a fluid distribution conduit 402 and valves 404, 406, 408,410, 412, 414, 416, 418, 420, 422. Fluid dispensing apparatus 400 may beused, for example, in combination with or as part of fluid dispensingapparatus 10 (e.g., as spray boom 24). Fluid dispensing apparatus 400includes a first valve 404, a second valve 406, a third valve 408, afourth valve 410, a fifth valve 412, a sixth valve 414, a seventh valve416, an eighth valve 418, a ninth valve 420, and a tenth valve 422. Eachvalve 404, 406, 408, 410, 412, 414, 416, 418, 420, 422 is positionablebetween a first, open position, in which fluid is allowed to flowthrough the valve, and a second, closed position, in which fluid flowthrough the valve is restricted. Each valve 404, 406, 408, 410, 412,414, 416, 418, 420, 422 may move between the first position and thesecond position when the valve is actuated. The valves 404, 406, 408,410, 412, 414, 416, 418, 420, 422 are separated into a first subsetincluding five valves and a second subset including five valves.Specifically, the first subset includes first valve 404, third valve408, fifth valve 412, seventh valve 416, and ninth valve 420, and thesecond subset includes second valve 406, fourth valve 410, sixth valve414, eighth valve 418, and tenth valve 422.

FIG. 7 is a graph 401 of positions of valves 404, 406, 408, 410, 412,414, 416, 418, 420, 422 versus time for fluid dispensing apparatus 400(shown in FIG. 6) using a conventional phase offset. With reference toFIGS. 6 and 7, first valve 404, third valve 408, fifth valve 412,seventh valve 416, and ninth valve 420 are simultaneously actuated inthe first subset (indicated by line 424) and moved between the firstposition and the second position. Accordingly, first valve 404, thirdvalve 408, fifth valve 412, seventh valve 416, and ninth valve 420 arein the first position at the same time, and actuated into the secondposition at the same time. In addition, second valve 406, fourth valve410, sixth valve 414, eighth valve 418, and tenth valve 422 aresimultaneously actuated in the second subset (indicated by line 426) andmoved between the first position and the second position. Accordingly,second valve 406, fourth valve 410, sixth valve 414, eighth valve 418,and tenth valve 422 are in the first position at the same time, andactuated into the second position at the same time. Moreover, becausethe duty cycle of the valves is less than 50%, valves 404, 406, 408,410, 412, 414, 416, 418, 420, 422 are simultaneously in the secondposition for a duration of time.

FIG. 8 is a graph 403 of positions of valves 404, 406, 408, 410, 412,414, 416, 418, 420, 422 versus time for fluid dispensing apparatus 400(shown in FIG. 6) using a phase offset 436 and a sub-phase offset 440.With reference to FIGS. 6 and 8, first valve 404 (indicated by line428), third valve 408 (indicated by line 429), fifth valve 412(indicated by line 431), seventh valve 416 (indicated by line 433), andninth valve 420 (indicated by line 435) are sequentially actuated out ofphase from one another by the sub-phase offset 440 according to a dutycycle and period. Second valve 406 (indicated by line 430), fourth valve410 (indicated by line 437), sixth valve 414 (indicated by line 439),eighth valve 418 (indicated by line 441), and tenth valve 422 (indicatedby line 443) are sequentially actuated out of phase from one another bythe sub-phase offset 440 according to the same duty cycle and period asthe first subset, and actuated out-of-phase from a preceding valve inthe first subset by the phase offset 436. Accordingly, each valve 404,406, 408, 410, 412, 414, 416, 418, 420, 422 is actuated and held in thefirst position and the second position at a period of time that isdifferent from other valves 404, 406, 408, 410, 412, 414, 416, 418, 420,422 in the same subset and in the other subset(s).

For example, first valve 404 is actuated at a first time 432 to allowfluid to flow out of distribution conduit 402. Second valve 406 isactuated at a second time 434 to allow fluid to flow out of distributionconduit 402. Second time 434 is offset from first time 432 by the phaseoffset 436. Third valve 408 is actuated at a third time 438 to allowfluid to flow out of distribution conduit 402. Third time 438 is offsetfrom first time 432 by the sub-phase offset 440. In addition, fourthvalve 410 is actuated at a fourth time 442 to allow fluid to flow out ofdistribution conduit 402. Fourth time 442 is offset from the third time438 by the phase offset 436, and from the second time 434 by sub-phaseoffset 440.

Also, first valve 404 is actuated at a fifth time 444 from the firstposition to the second position to restrict fluid flow out ofdistribution conduit 402. Second valve 406 is actuated at a sixth time446 from the first position to the second position. Sixth time 446 isoffset from fifth time 444 by phase offset 436. Third valve 408 isactuated at a seventh time 448 from the first position to the secondposition. Seventh time 448 is offset from fifth time 444 by sub-phaseoffset 440. Fourth valve 410 is actuated at an eighth time 450 from thefirst position to the second position. Eighth time 450 is offset fromsixth time 446 by sub-phase offset 440 and offset from seventh time 448by phase offset 436.

In the illustrated embodiment, sub-phase offset 440 is less than phaseoffset 436. For example, sub-phase offset 440 may be in a range of about1 millisecond (ms) to about 10 ms and phase offset 436 may be in a rangeof about 2 ms to about 100 ms. In this embodiment, phase offset 436 isapproximately 50 ms and sub-phase offset 440 is approximately 10 ms.Phase offset 436 may be determined by dividing the cycle time (100 ms)by the number of subsets (2). Sub-phase offset 440 may be determined bydividing the cycle time (100) by the number of valves (10). Inalternative embodiments, phase offset 436 and sub-phase offset 440 maybe determined (e.g., by controller 318) in any suitable manner thatenables fluid dispensing apparatus 400 to function as described herein.

FIG. 9 is a plot 405 showing the instantaneous number of open valvesversus time during operation of fluid dispensing apparatus 400 (shown inFIG. 6) using (i) only phase offset 436 and (ii) phase offset 436 andsub-phase offset 440. In reference to FIG. 9, curve 451 represents theinstantaneous number of open valves for fluid dispensing apparatus 400including phase offset 436. Curve 451 includes peaks 452 which occurwhen the first subset of valves are open and when the second subset ofvalves are open. Between peaks 452, curve 451 indicates that all valvesare in a closed position.

Curve 454 represents the instantaneous number of open valves of fluiddispensing apparatus 400 including phase offset 436 and sub-phase offset440. Curve 454 has a slope of zero indicating that the number of valvesopen at a given time remains constant during operation of fluiddispensing apparatus 400 due to phase offset 436 and sub-phase offset440. In other embodiments, curve 454 may have relatively slightvariations, where the number of open valves increases or decreases. Forexample, the number of open valves may increase or decrease by a singlevalve based on the relationship between the sub-phase offset, the dutycycle, and the cycle time of the valve assemblies 36. In contrast, intwo-phase systems, the number of open valves decreases and increases byhalf the total number valves, as shown by curve 451.

FIG. 10 is a graph 407 of positions of valves 404, 406, 408, 410, 412,414, 416, 418, 420, 422 versus time for fluid dispensing apparatus 400(shown in FIG. 6) including phase offset 436 and each valve 404, 406,408, 410, 412, 414, 416, 418, 420, 422 operating at sixty percent dutycycle. With reference to FIGS. 6 and 10, first valve 404, third valve408, fifth valve 412, seventh valve 416, and ninth valve 420 aresimultaneously actuated in the first subset (indicated by line 456) andmoved between the first position and the second position. Accordingly,first valve 404, third valve 408, fifth valve 412, seventh valve 416,and ninth valve 420 are in the first position at the same time, andactuated in to the second position at the same time. In addition, secondvalve 406, fourth valve 410, sixth valve 414, eighth valve 418, andtenth valve 422 are simultaneously actuated in the second subset(indicated by line 458) and moved between the first position and thesecond position. Accordingly, second valve 406, fourth valve 410, sixthvalve 414, eighth valve 418, and tenth valve 422 are in the firstposition at the same time, and actuated in to the second position at thesame time. Moreover, because the duty cycle of the valves is greaterthan 50%, all of valves 404, 406, 408, 410, 412, 414, 416, 418, 420, 422are in the first position for a duration of time.

FIG. 11 is a graph 409 of positions of valves 404, 406, 408, 410, 412,414, 416, 418, 420, 422 versus time for fluid dispensing apparatus 400(shown in FIG. 6) including a phase offset 436 and a sub-phase offset440, and each valve 404, 406, 408, 410, 412, 414, 416, 418, 420, 422operating at a sixty percent duty cycle. With reference to FIGS. 6 and11, first valve 404 (indicated by line 460), third valve 408 (indicatedby line 461), fifth valve 412 (indicated by line 463), seventh valve 416(indicated by line 465), and ninth valve 420 (indicated by line 467) aresequentially actuated out of phase from one another by the sub-phaseoffset 440. Second valve 406 (indicated by line 462), fourth valve 410(indicated by line 470), sixth valve 414 (indicated by line 472), eighthvalve 418 (indicated by line 474), and tenth valve 422 (indicated byline 476) are sequentially actuated out of phase from one another by thesub-phase offset 440, and actuated out-of-phase from a preceding valvein the first subset by the phase offset 436. Accordingly, each valve404, 406, 408, 410, 412, 414, 416, 418, 420, 422 is actuated and held inthe first position and the second position at a period of time that isdifferent from other valves 404, 406, 408, 410, 412, 414, 416, 418, 420,422 in the same subset and in the other subset(s).

FIG. 12 is a plot 411 showing the instantaneous number of open valvesversus time for fluid dispensing apparatus 400 (shown in FIG. 6) using(i) only phase offset 436 and (ii) phase offset 436 and sub-phase offset440, for valves operated at a 60% duty cycle. In reference to FIGS. 6and 12, curve 464 represents the number of open valves for fluiddispensing apparatus 400 using only phase offset 436 and a sixty percentduty cycle. Curve 464 includes peaks 466, corresponding to a point intime when the first subset of valves and the second subset of valves arein the first, open position. In addition, curve 464 includes valleys 468which correspond to a point in time when one of the first subset and thesecond subset of valves 404, 406, 408, 410, 412, 414, 416, 418, 420, 422is in the first, open position, and the other of the first subset andthe second subset of valves 404, 406, 408, 410, 412, 414, 416, 418, 420,422 is in the second, closed position.

Plot 411 also includes a curve 469 representing the instantaneous numberof open valves for fluid dispensing apparatus 400 using phase offset 436and sub-phase offset 440, and sixty percent duty cycle. Curve 469 has aslope of zero indicating that the number of open valves is constantduring operation of fluid dispensing apparatus 400 due to phase offset436 and sub-phase offset 440. Thus, although each valve 404, 406, 408,410, 412, 414, 416, 418, 420, 422 is being cyclically actuated betweenopen and closed positions according to a duty cycle during operation offluid dispensing apparatus 400, the overall number of valves that areopen at a given time remains the same or varies by a single valve. Thus,utilizing a sub-phase offset avoids large discrepancies in the number ofvalves that are opened or closed at a given time, and thereby providesimproved operating efficiency and accuracy. In particular, bymaintaining a relatively constant number of opened valves duringoperation, large variations in instantaneous pressure and fluid flow arereduced or eliminated, and spikes in electrical power consumption arealso reduced or eliminated.

Further reductions in peak power consumption and overall average powerconsumption can also be realized by utilizing specific drive circuitsand driving techniques. For example, FIG. 13 is a schematic diagram of adrive circuit 1300 for use in driving solenoid valves, such as, forexample, solenoid valve 300, shown in FIG. 3. Drive circuit 1300 mayform all or part of controller 318, shown in FIG. 3 and FIG. 4.Generally, drive circuit 1300 is configured to generate a currentsignal, or waveform, for energizing a solenoid coil 1302 of the solenoidvalve. Drive circuit 1300 includes a field-effect transistor (FET) 1304configured to open and close the circuit for energizing solenoid coil1302. More specifically, FET 1304 opens and closes a path to ground(GND) through which a coil current conducts from a voltage supply,V_(coil), through solenoid coil 1302, and to GND through FET 1304.Generally, FET 1304 is controlled, i.e., open and closed, by applying avoltage to a gate 1306 of FET 1304. FET 1304 is controlled by a gatesignal 1308 provided by a controller, such as controller 318, forexample. In certain embodiments, gate signal 1308 is a simplelogic-level signal that applies a high logic level to gate 1306 to makeFET 1304 conduct the coil current when the solenoid valve should open.Likewise, in such an embodiment, gate signal 1308 applies a low logiclevel to gate 1306 to make FET 1304 open the circuit and de-energizesolenoid coil 1302.

In other embodiments, gate signal 1308 is pulse-width modulated (PWM)with a certain duty cycle and at a certain frequency to supply a desiredamount of current to solenoid coil 1302. For example, a 100% duty cyclegate signal 1308 may be applied to gate 1306 to transition the solenoidvalve from a closed position to an opened position, i.e., to translatethe poppet from the closed position to the opened position. A 0% dutycycle gate signal 1308 is applied to gate 1306 (or gate signal 1308 isremoved entirely) to transition the solenoid valve from the openedposition to the closed position. Further, gate signal 1308 is modulatedto a high frequency and a low duty cycle when the solenoid valve isbeing held in the opened position after transitioning from the closedposition. In certain embodiments, when the solenoid valve is being heldin the closed position, gate signal 1308 may be modulated to a lowfrequency and low duty cycle to maintain a level of coil current abovezero, but below the threshold at which the valve poppet would translatefrom the closed position to the opened position, thereby improvingresponsiveness of the valve to an “open” command.

Drive circuit 1300 includes a protection diode 1310 connected inparallel to FET 1304 to protect FET 1304 from large voltage spikes thatwould otherwise develop on the drain terminal of FET 1304, representedby a node 1312 in FIG. 13, when periodically switching the coil current.More specifically, when switching the coil current off, a (negative)back electromotive voltage, or “electromotive force” (EMF), develops atnode 1312 that “opposes” the change in current in solenoid coil 1302,i.e., to decay to zero. Protection diode 1310 provides an alternativepath to GND for the coil current dissipating from solenoid coil 1302,thereby preventing an excessive voltage buildup on node 1312. Protectiondiode 1310 may be, for example, a Zener diode having a high breakdownvoltage of about 28 volts or, in other embodiments, about 40 volts.Protection diode 1310 should be selected to have a breakdown voltagesufficiently low to protect FET 1304 from a voltage that could saturateor damage FET 1304, while also being high enough to not conduct when FET1304 is open. Further, the breakdown voltage of protection diode 1310should be high enough to generate a sufficiently large reverse voltageat node 1312 to quickly dissipate energy stored in solenoid coil 1302when translating the poppet to the closed position.

Drive circuit 1300 includes a flyback circuit 1314 that slows the decayof current through solenoid coil 1302 when switched off at a highfrequency by FET 1304. By slowing the decay, flyback circuit 1314enables the coil current to remain substantially constant, and above athreshold at which the valve would close, when switching FET 1304 at ahigh frequency, e.g., when the valve is being held in the openedposition by a high frequency PWM gate signal 1308. Flyback circuit 1314includes a diode 1316 that preferably has a low forward voltage, such asa silicon or germanium diode, or a Schottky diode. Generally, the speedat which solenoid coil 1302 discharges its stored energy is directlyrelated to the voltage drop across it, which is further a function ofthe back EMF. Accordingly, the lower the forward voltage of diode 1316,the lower the voltage drop across solenoid coil 1302, and the slowerenergy is dissipated from solenoid coil 1302. Flyback circuit 1314further includes a FET 1318 that enables and disables flyback circuit1314 by closing and opening the “free-wheeling” path for the coilcurrent to dissipate from node 1312 through diode 1316. FET 1318 iscontrolled by a gate signal 1320 applied to a gate 1322 of FET 1318.Gate signal 1320 is supplied by a controller, such as, for example,controller 318, or the controller that operates FET 1304 using gatesignal 1308, described above. FET 1318 and gate signal 1320 enableflyback circuit 1314 when FET 1304 is operated with a high frequency PWMsignal, such as when the valve is being held in an opened position.While enabled, flyback circuit 1314 and, more specifically, diode 1316slow the decay of the coil current from solenoid coil 1302, furtherenabling the reduction of the duty cycle of current supplied to solenoidcoil 1302, i.e., the duty cycle of gate signal 1308. Likewise, FET 1318and gate signal 1320 disable flyback circuit 1314 when the coil currentshould dissipate quickly, such as when the valve is to be closed. Whenflyback circuit 1314 is disabled, protection diode 1310 directs thecurrent to GND. Generally, flyback circuit 1314 may be enabled ordisabled when transitioning the valve from the closed position to theopened position using a 100% duty cycle gate signal 1308, becausesolenoid coil 1302 is charging and FET 1304 provides a low-impedancepath to GND.

FIG. 14 is a schematic diagram of another drive circuit 1400 for use indriving multiple solenoid valves and, particularly, phased solenoidvalves. Drive circuit 1400 is configured to operate two sets, orsub-sets, of valves out of phase from each other, which is to say thetwo sets of valves are opened and closed offset in time with respect toeach other. The valves (for clarity, only the solenoid coils of thevalves are shown in FIG. 14) and, more specifically, their respectivesolenoid coils 1402 and 1404 are supplied a coil voltage (Vcoil) fromcoil voltage supply 1406, and the coil currents are conducted throughthe solenoid coils 1402 and 1404 to respective ground paths 1408 and1410 for a first phase (PH1) valve set and a second phase (PH2) valveset. Generally, when the PH1 ground path 1408 is closed, the PH1solenoid coils 1402 conduct coil currents from coil voltage supply 1406to GND and, likewise, when the PH2 ground path 1410 is closed, the PH2solenoid coils 1404 conduct coil currents from coil voltage supply 1406to GND.

The PH1 ground path 1408 and PH2 ground path 1410 are opened and closedby a FET 1412 and a FET 1414, respectively. In alternative embodiments,FET 1412 and FET 1414 may be coupled in series between solenoid coils1402 and 1404 and coil voltage supply 1406. FET 1412 and FET 1414 may becontrolled directly or by respective gate driver circuits (not shown) inresponse to a PH1 control signal 1416 and a PH2 control signal 1418,respectively. In the embodiment of FIG. 14, FET 1412 and FET 1414 areillustrated as being controlled directly by PH1 control signal 1416 andPH2 control signal 1418, respectively.

PH1 control signal 1416 is applied to a gate 1420 of FET 1412 tocontrol, or gate, FET 1412. FET 1412 generally enables fast turn-on andis capable of sinking coil currents conducted by solenoid coils 1402. Inalternative embodiments, where FET 1412 is coupled in series betweensolenoid coils 1402 and coil voltage supply 1406, FET 1412 sources coilcurrents conducted by solenoid coils 1402. FET 1412 may be a powermetal-oxide semiconductor field-effect transistor (MOSFET), an insulatedgate bipolar transistor (IGBT), or other solid state device suitable forswitching the coil current. PH1 control signal 1416 may be provided, incertain embodiments, by controller 318 (shown in FIG. 3) or any othersuitable controller or digital circuit.

PH2 control signal 1418 is applied to a gate 1422 of FET 1414 tocontrol, or gate, FET 1414. FET 1414 generally enables fast turn-on andis capable of sinking coil currents conducted by solenoid coils 1404. Inalternative embodiments, where FET 1414 is coupled in series betweensolenoid coils 1404 and coil voltage supply 1406, FET 1414 sources coilcurrents conducted by solenoid coils 1404. FET 1414 may be a powerMOSFET, an IGBT, or other solid state device suitable for switching thecoil current. PH2 control signal 1418 may be provided, in certainembodiments, by controller 318 (shown in FIG. 3) or any other suitablecontroller or digital circuit.

Drive circuit 1400 includes protection diodes 1424 and 1426 connected inparallel to FETs 1412 and 1414, respectively. Protection diodes 1424 and1426 are similar in structure and function to protection diode 1310,shown in FIG. 13. More specifically, protection diode 1424 for example,protects FET 1412 from excessive voltage build up across the terminalsof FET 1412 when FET 1412 is opened by dissipating current generatedfrom the energy stored in the PH1 solenoid coils 1402. Protection diode1426 for example, protects FET 1414 from excessive voltage build upacross the terminals of FET 1414 when FET 1414 is opened by dissipatingcurrent generated from the energy stored in the PH1 solenoid coils 1404.Protection diodes 1424 and 1426 may include, for example, one or moreZener diodes having a breakdown voltage of about 28 volts or, in otherembodiments, about 40 volts.

Drive circuit 1400 includes flyback circuits 1428 and 1430 connected inparallel to the PH1 and PH2 solenoid coils 1402 and 1404, respectively.Flyback circuits 1428 and 1430 are similar in structure and function toflyback circuit 1314, shown in FIG. 13. More specifically, flybackcircuit 1428 for example, slows the dissipation of coil currents fromthe PH1 solenoid coils 1402 when FET 1412 is switched at a highfrequency. Flyback circuit 1428 includes a diode 1432 coupled in serieswith a MOSFET 1434, and flyback circuit 1428 is coupled between coilvoltage supply 1406 and the PH1 ground path 1408. When enabled, diode1432 “free-wheels” the stored coil energy in the PH1 solenoid coils1402, i.e., free-wheeling initiates immediately when FET 1412 is openedand continues for a limited duration after FET 1412 is opened. Diode1432 is preferably a low forward voltage diode, such as a Schottkydiode, a silicon diode, or a germanium diode. A lower forward voltageenables a slower dissipation of the coil current and, consequently, amore-steady coil current as FET 1412 is switched at a high frequency. Inalternative embodiments, where FET 1414 is coupled in series betweensolenoid coils 1404 and coil voltage supply and FET 1414 sources coilcurrents, flyback circuit 1428 (and/or protection diodes 1424 and 1426)are modified based on the opposite direction of the “flyback current.”

Flyback circuit 1428, in certain embodiments, may further include a gatedriver circuit (not shown) for gating MOSFET 1434. Alternatively, asshown in FIG. 14, MOSFET 1434 is enabled and disabled directly by aflyback control signal 1436 applied at a gate 1438 of MOSFET 1434.

Flyback control signal 1436 may be supplied, in certain embodiments, bycontroller 318 or any other suitable controller or digital circuit.Generally, flyback control signal 1436 enables flyback circuit 1428 whenthe PH1 valve set and, more specifically, the PH1 solenoid coils 1402are being supplied a high frequency PWM current signal by FET 1412, suchas, for example, when the PH1 valve set is being held in the openedposition. Further, flyback control signal 1436 disables flyback circuit1428 when the coil currents in the PH1 solenoid coils 1402 should bedissipated quickly, such as, for example, when the PH1 valve set istransitioning from the opened position to the closed position.

Likewise, flyback circuit 1430 slows the dissipation of coil currentsfrom the PH2 solenoid coils 1404 when FET 1414 is switched at a highfrequency. Flyback circuit 1430 includes a diode 1440 coupled in serieswith a MOSFET 1442, and flyback circuit 1430 is coupled between coilvoltage supply 1406 and the PH2 ground path 1410. When enabled, diode1440 “free-wheels” the stored coil energy in the PH2 solenoid coils1404, i.e., free-wheeling initiates immediately when FET 1414 is openedand continues for a limited duration after FET 1414 is opened. Diode1440 is preferably a low forward voltage diode, such as a Schottkydiode, a silicon diode, or a germanium diode. A lower forward voltageenables a slower dissipation of the coil current and, consequently, amore-steady coil current as FET 1414 is switched at a high frequency.Flyback circuit 1430, in certain embodiments, may further include a gatedriver circuit (not shown) for gating MOSFET 1442. Alternatively, asshown in FIG. 14, MOSFET 1442 is enabled and disabled directly by aflyback control signal 1444 applied at a gate 1446 of MOSFET 1442.

Flyback control signal 1444 may be supplied, in certain embodiments, bycontroller 318 (shown in FIG. 3) or any other suitable controller ordigital circuit. Generally, flyback control signal 1444 enables flybackcircuit 1430 when the PH2 valve set and, more specifically, the PH2solenoid coils 1404 are being supplied a high frequency PWM currentsignal by FET 1414, such as, for example, when the PH2 valve set isbeing held in the opened position. Further, flyback control signal 1444disables flyback circuit 1430 when the coil currents in the PH2 solenoidcoils 1404 should be dissipated quickly, such as, for example, when thePH2 valve set is transitioning from the opened position to the closedposition.

Although systems and methods are described above with reference to anagricultural fluid dispensing apparatus, embodiments of the presentdisclosure are suitable for use with agricultural fluid applicationsystems other than fluid dispensing apparatus. In some embodiments, forexample, the systems and methods of the present disclosure areimplemented in a fluid application system that injects fluid, such asfertilizer, into the soil through dispensing tubes, rather than nozzles.In yet other embodiments, systems and methods of the present disclosuremay be implemented in any system, whether commercial, industrial orresidential, that utilizes valves connected to a distribution conduit ordistribution manifold, such as irrigation systems.

The systems and methods described herein provide for phased pulsing ofvalves of a fluid dispensing apparatus. For example, in fluid dispensingapparatus within which the systems and methods may be embodied orcarried out, actuation of valves may be separated by a phase offset anda sub-phase offset. Accordingly, the operating efficiency and accuracyof the fluid dispensing apparatus may be increased. In addition,variations in instantaneous flow within a distribution conduit of thefluid dispensing apparatus may be reduced. Also, fluctuations inelectrical current required to regulate the valves is reduced. As aresult, the cost to operate and maintain the fluid dispensing apparatusmay be decreased. Further, as described above, current supplied torespective solenoid coils of the valves may be pulse-width modulated(PWM) to improve power efficiency and, moreover, may be combined with acontrolled flyback circuit to further reduce average power consumptionof the respective solenoid coils. In yet other embodiments of thesystems and methods described herein, utilizing sub-phase offsets, PWMenergizing of the solenoid coils, and controlled flyback circuits mayall be combined to achieve reduction in peak power consumption, betterdistribution of power consumption over time, and overall reduction inaverage power consumption by a given valve. Further, in such acombination, the valves would exhibit improved operating efficiency ofnozzle assemblies and mitigation of problems associated with varyinginstantaneous fluid flow, including water hammer, pressure fluctuations,and flowmeter inconsistencies.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other and examples areintended to be within the scope of the claims if they include structuralelements that do not differ from the literal language of the claims, orif they include equivalent structural elements with insubstantialdifferences from the literal language of the claims.

What is claimed:
 1. A solenoid valve comprising: a solenoid coil; a poppet configured to transition within the solenoid valve between a first position and a second position based on a coil current flowing through the solenoid coil; and a drive circuit comprising: a first semiconductor device controlled by a gate signal to control the coil current; and a flyback circuit coupled with the solenoid coil, the flyback circuit comprising a second semiconductor device in series with a diode, wherein the second semiconductor device is controlled by a flyback control signal to: (i) enable the flyback circuit to maintain the coil current through the solenoid coil above a threshold value by recirculating the coil current through the solenoid coil, the second semiconductor device, and the diode when the first semiconductor device is controlled by the gate signal to transition the poppet to the second position, and (ii) disable recirculation of the coil current through the solenoid coil when the first semiconductor device is controlled by the gate signal to transition the poppet to the first position; and a controller configured to transition the poppet from the first position to the second position using the gate signal, to enable the flyback circuit using the flyback control signal, and to reduce at least one of a duty cycle of the gate signal and a frequency of the gate signal when the flyback circuit is enabled.
 2. The solenoid valve of claim 1, wherein the controller is further configured to transition the poppet from the second position to the first position using the gate signal, and to disable the flyback circuit using the flyback control signal.
 3. The solenoid valve of claim 2, wherein the controller is further configured to generate the gate signal having a zero percent duty cycle to transition the poppet from the second position to the first position.
 4. The solenoid valve of claim 1, wherein the flyback circuit is coupled in parallel with the solenoid coil to form a closed-loop circuit that excludes the first semiconductor device.
 5. The solenoid valve of claim 1, wherein the controller is further configured to generate the gate signal with an initial duty cycle of 100 percent to transition the poppet from the first position to the second position.
 6. The solenoid valve of claim 1, wherein: the gate signal comprises a pulse-width modulated (PWM) gate signal, and the controller is further configured to reduce the duty cycle of the PWM gate signal to 25 percent or less when the flyback circuit is enabled.
 7. The solenoid valve of claim 1, wherein: the first position corresponds to a closed position of the solenoid valve, and the second position corresponds to an open position of the solenoid valve.
 8. A method for controlling a solenoid valve having a solenoid coil and a poppet configured to transition within the solenoid valve, the method comprising: transitioning the poppet from a first position to a second position using a gate signal applied to a first semiconductor device coupled with the solenoid coil, wherein the first semiconductor device is controlled by the gate signal to control a coil current flowing through the solenoid coil; enabling a flyback circuit coupled with the solenoid coil, the flyback circuit including a second semiconductor device in series with a diode, wherein enabling the flyback circuit maintains the coil current through the solenoid coil above a threshold value by recirculating the coil current through the solenoid coil, the second semiconductor device, and the diode; and reducing at least one of a duty cycle of the gate signal and a frequency of the gate signal when the flyback circuit is enabled.
 9. The method of claim 8, further comprising: transitioning the poppet from the second position to the first position using the gate signal; and disabling the flyback circuit to disable recirculation of the coil current through the solenoid coil.
 10. The method of claim 9, wherein transitioning the poppet from the second position to the first position comprises generating a zero percent duty cycle gate signal.
 11. The method of claim 8, wherein transitioning the poppet from the first position to the second position comprises generating a 100 percent duty cycle gate signal.
 12. The method of claim 8, wherein: the gate signal comprises a pulse-width modulated (PWM) gate signal, and reducing at least one of the duty cycle of the gate signal and the frequency of the gate signal when the flyback circuit is enabled comprises reducing the duty cycle of the PWM gate signal to 25 percent or less when the flyback circuit is enabled.
 13. The method of claim 8, wherein transitioning the poppet from the first position to the second position comprises transitioning the solenoid valve from a closed position to an open position.
 14. A drive circuit for controlling a solenoid valve having a solenoid coil, the drive circuit comprising: a first semiconductor device controlled by a pulse-width modulated (PWM) gate signal to energize the solenoid coil and transition the solenoid valve from a first position to a second position; a flyback circuit coupled with the solenoid coil, the flyback circuit comprising: a second semiconductor device controlled by a flyback control signal to: (i) enable the flyback circuit when the first semiconductor device is controlled by the PWM gate signal to hold the solenoid valve in the second position, and (ii) disable the flyback circuit when the first semiconductor device is controlled by the PWM gate signal to transition the solenoid valve to the first position; and a diode coupled in series with the second semiconductor device to slow a decay of a current conducted through the solenoid coil while the solenoid valve is in the second position; and a controller configured to generate the PWM gate signal to transition the solenoid valve from the first position to the second position, to enable the flyback circuit using the flyback control signal, and to reduce a duty cycle of the PWM gate signal when the flyback circuit is enabled.
 15. The drive circuit of claim 14, wherein the controller is further configured to generate the PWM gate signal to transition the solenoid valve from the second position to the first position, and to disable the flyback circuit using the flyback control signal.
 16. The drive circuit of claim 15, wherein the controller is further configured to generate the PWM gate signal having a zero percent duty cycle to transition the solenoid valve from the second position to the first position.
 17. The drive circuit of claim 14, wherein the flyback circuit is coupled in parallel with the solenoid coil to form a closed-loop circuit that excludes the first semiconductor device.
 18. The drive circuit of claim 14, wherein the controller is further configured to generate the PWM gate signal with an initial duty cycle of 100 percent to transition the solenoid valve from the first position to the second position.
 19. The drive circuit of claim 14, wherein: the first position of the solenoid valve corresponds to a closed position for the solenoid valve, and the second position of the solenoid valve corresponds to an open position for the solenoid valve.
 20. The drive circuit of claim 14, wherein the controller is further configured to control the duty cycle of the PWM gate signal to maintain the current through the solenoid coil above a threshold value corresponding with the solenoid valve being held in the second position. 